The differentiation of neurons, the acquisition of specific neuronal shapes and the formation of synapses are regulated by interactions of neurons with other cells and components of extracellular matrices. Our preliminary results implicate a cell surface heparan sulfate proteoglycan (HSPG) in FN-mediated neuronal cell adhesion and neurite outgrowth. In these studies, we have identified a synthetic heparin binding Peptide from Fibronectin (FN) which promotes the adhesion of a neuronal cell line, B104, and promotes neurite outgrowth from dorsal root ganglion and spinal cord neurons from chick embryos. We propose to use the neuroblastoma cells and primary neurons to further define the molecular bases for proteoglycanmediated neuronal cell adhesion to the 33 kD heparin binding fragment of FN. Specifically, we propose: 1 . To use overlapping synthetic peptides to further define the heparin/proteoglycan binding and cell adhesion promoting activity of FN-C/H 11. 2. To isolate cell surface HSPG from B 1 04 neuroblastoma cells and to generate polyclonal and monoclonal antibodies against this HSPG. 3. To use anti-HSPG polyclonal and monoclonal antibodies to partially characterize HSPG expressed by neuroblastoma cell lines. 4. To use anti-core protein antibodies to determine the localization and functions of core protein on neurons in fetal and neonatal nervous system. These studies will include examination of the in vitro distribution of HSPG on specific cell types and on cell bodies, neurites, growth cones, determination of spatial and temporal correlations in vivo, and experiments to assess the function of the HSPG in neuronal interactions with fibronectin.